MAGNETIC-PROPERTIES OF MODIFIED BA-FERRITE PARTICLES

Modification with magnetite on Ba-ferrite particles was carried out by heating alkaline suspension including Ba-ferrite particles and Fe2+ h ydroxides as described by Kiyama et al. [J. Solid State Chem. 99, 329 (1992)] to get higher magnetization. As a result of x-ray powder diffr action measurements, reflection intensity of magnetoplumbite phase dec reases and that of spinel phase increases with increase of Fe2+ quanti ty added, simultaneously. Coercive force goes down and magnetization i ncreases as Fe2+ quantity added increases. The differential hysteresis loop of the mixed samples (Ba-ferrite particles and magnetite particl es) has two peaks. And that of the modified samples has only one peak. From these results, it becomes clear that there exists strong magneti c interaction between Ba-ferrite core and magnetite shell. The measure ments of temperature dependence of magnetization at the applied field of about 16.5 kA/m shows that the Hopkinson peak shifts toward higher temperature with increase of the modified amount. It also indicates th e strong magnetic interaction between core and shell materials.